This invention relates generally to apparatus for applying lubricant to frictional surfaces and more particularly to apparatus for automatically metering the lubricant to the surface in accordance with the need therefor.
Automatic lubrication systems are well known in the art. These systems have been devised to reduce the need for maintenance personnel and to provide continuous protection during the operation of the mechanisms. The known systems, however, frequently have not been satisfactory because of two primary disadvantages; some systems apply lubricant at fixed intervals which are not a function of the need, and other systems are not sufficiently sensitive to apply the lubricant at the immediate time of need.
Representative of the first group are those systems which supply lubricant according to a count or at different rates depending upon the velocity of the mechanism. U.S. Pat. No. 3,856,114 is of this type in that lubricant application varies in accordance with the feed rate of a mechanism. Such control systems require careful and frequent calibration to insure that a sufficient and yet not excessive amount of lubricant is applied. Other techniques have used a fixed amount of operating time to actuate the lubrication mechanism.
Other patents relating to the second group, such as U.S. Pat. Nos. 3,463,268 and 3,674,112, respectively sense an increase in driving power or an increase in the bearing temperature to provide actuating signals for the lubricating devices. These arrangements have the weakness that they fail to differentiate between either changes in loads on the mechanism or changes in environmental temperature. Hence, they lack the sensitivity to apply lubricant at the most appropriate times to minimize wear or damage.